1. Field of the Invention
This invention relates to liquid injection recording apparatus, and more particularly to an apparatus in which recording liquid is discharged from an orifice onto a recording medium by discharge energy generating means to make flying liquid droplets, thereby accomplishing recording.
2. Related Background Art
In the heretofore known liquid injection recording apparatus such as, for example, the bubble jet (BJ) type recording apparatus (U.S. Pat. No. 4,723,129, etc.), it is known that the recording head used therein comprises a plurality of layers of materials or members (e.g. U.S. Pat. Nos. 4,417,251, 4,394,670, 4,521,787, etc. ). In FIG. 1 of the accompanying drawings, there is shown an example of the layered state of such a recording head, wherein silicon (Si) is used for a substrate 1, a silica (SiO.sub.2) layer 2 is provided thereon. A dry film layer 4 of acrylic resin including a nozzle 3 formed by photolithography and a glass layer 5 are further layered thereon (a discharge energy generating element is omitted). In the recording head thus constructed, when an electrical signal is supplied to discharge energy generating means, a bubble is created in a BJ type liquid path. Recording liquid is thus discharged from a discharge port 6 by a liquid droplet which flies out in the direction of arrow A.
In the conventional recording head as described above constructed of layers of a plurality of kinds of different materials as described above, wettability differs on the discharge port surface 7 (the surface in which the discharge port is disposed). For example, wettability is higher on the SiO.sub.2 than on the other layers. Thus, particularly when the frequency of the electrical signal is increased, the drop 8 is "pulled" by a member which is formed of a material of good wettability as shown in FIG. 2. Therefore the liquid droplet (not shown) discharged from the discharge port 6 is pulled toward the drop 8 as indicated by arrow B such that a large kink is produced in the scan direction, resulting in lowered recording performance (for example, U.S. Pat. No. 4,499,480).
In order to prevent the drop described above, it is conceivable to uniformize the surface roughness of the discharge port surface (U.S. Pat. No. 4,499,480), to form the discharge port surface of one and the same material (U.S. Pat. Nos. 4,521,787 and 4,417,251) or to coat the discharge port surface with a liquid-repellent substance, (U.S. Pat. No. 4,723,129). Especially, coating the discharge port surface with a liquid repellent substance can solve the drop problem both simply and effectively because it requires no change in the structure of the recording head itself. However, particularly in the recording head of the above-described construction, the discharge port surface is such that different materials are exposed, so it is difficult to choose a durable liquid repellant material. Thus, a method of occasionally manually applying a liquid-repellent material is also known.
However, manually coating the discharge port surface of the recording head with a liquid-repellent material as required takes much time and requires skill so that too much liquid-repellent material is not applied to the discharge port surface or unnecessarily enter the recording head through the discharge ports, and thus, is not preferable from the viewpoint of maintenance.
Moreover, even when the liquid-repellent process has been imparted on the discharge port surface, excess recording liquid has often adhered to and remained on the discharge port surface, and foreign materials such as dust and the like have sometimes adhered to the discharge port surface. Numerous methods to remove such excess recording liquid and foreign materials from the discharge port surface include wiping the discharge port surface by means of a plate member such as a rubber blade is very effective to solve the above-noted problem. However, since the plate member performs its wiping function by contacting the discharge port surface and being moved relative thereto, this has sometimes required choosing a material with high durability and wear resistance, rather than an optimal liquid-repellent or anti-stripping property. That is, it has been necessary to choose a material while taking into account the physical characteristic of the coating formed by the liquid-repellent process material, more than the congeniality between the material of the discharge port surface of the recording head and the liquid-repellent process material. This has led to great difficulty in choosing useful liquid-repellent substance.